CHEMICAL COMPOSITION OF THE BODY. 95 



MILK SUGAR, C^H^O,, + H,O, exists in the proportion of from 3 to 5 or 

 6 per cent, in the milk of various animals. It is feebly saccharine to the 

 taste, ami is gritty to the teeth. Like grape sugar it reduces the salts of 

 copper in an alkaline solution, and rotates the plane of polarization to the 

 right, 



GLYCOOEN, C,.H 10 O 5 (Liver sugar}. This remarkable substance was first 

 obtained by C. Bernard by immersing the livers of various animals, within 

 a few seconds of their death, in hot water, to coagulate the albumen, then 

 bruising the mass in a mortar and filtering the liquid through animal char- 

 coal. On the addition of alcohol or of glacial acetic acid, the glycogen is 

 precipitated as a white and tasteless amorphous material soluble in water, 

 but incapable of effecting the reduction of the salts of copper. Briicke 1 has 

 lately recommended the double iodide of mercury and potassium as the best 

 means of completely precipitating pure glycogen. The solution is prepared 

 by precipitating solution of corrosive sublimate with potassium iodide, wash- 

 ing the precipitate and dissolving it in hot solution of potassium iodide till 

 the latter is saturated with it. Pure glycogeu is obtained by first placing the 

 liver in boiling water, then bruising it in a mortar, returning it to the same 

 water, and boiling it for a few minutes; filtering and rapidly cooling the 

 solution with ice or a refrigerator. Hydrochloric acid and the mercurial 

 solution are then alternately added as long as any precipitate falls, the fluid 

 is filtered and spirit of wine added to the filtrate till an abundant precipitate 

 of glycogeu takes place. This is washed with weak alcohol and finally purified 

 with ether. Glycogeu thus obtained is free from nitrogen and leaves no ash 

 when burnt. It is colored red with iodine, not brown. It rotates the plane 

 of polarization to the right, Glycogeu was found by Briicke to be constantly 

 present in the muscles, but only very small traces of a substance, the identity 

 of which with glycogen was somewhat doubtful, could be obtained from the 

 blood, spleen, kidneys, or secreting mammary gland, so that it could not be 

 admitted that it was stored up in the body as a preliminary stage of the 

 formation of milk sugar. 



All muscles yield sugar, part of which appears to present identity of 

 composition with grape and liver sugar, whilst part possesses distinctive 

 characters, and has received the name of Inosite. Weiss 2 found that mus- 

 cular activity was associated with a marked decrease in the percentage of 

 glycogeu in the case of frogs, amounting to a quarter of the total normal 

 quantity. The heart, however, in spite of its constant activity, contains 

 (in the dog) two-thirds as much glycogen as ordinary muscular flesh. 



INOSITE, C 6 H, 2 O fi + 2H 8 O, is a kind of sugar which has been found in the 

 expressed muscle-juice of the heart; in the pancreas and thymus glands; in 

 the lungs, kidneys, liver, and spleen ; 3 in the brain (Muller) and suprarenal 

 capsules of the ox. In disease, as in diabetes and Bright's disease, it oc- 

 curs in the urine. It is identical with the Phaseomannite found in beans, 

 and is found elsewhere in the vegetable kingdom. It crystallizes in long 

 rhombohedra, which are at first transparent but subsequently become opaque. 

 It possesses a feebly saccharine taste, and has no power of rotating the 

 plane of polarized light, nor does it, like some other kinds of sugar, reduce 

 the salts of bismuth, copper, or silver in an alkaline solution. A good test 

 for it, suggested by Scherer, consists in heating to dryness the supposed mass 

 with a little nitric acid in a porcelain dish, then moistening it with chloride 

 of calcium, and again evaporating it, when a rose-red mass remains. It does 

 not undergo alcoholic fermentation, but when in contact with decomposing 

 albuminous bodies it yields lactic and butyric acids. 



1 Wien. Akad. Ber., Band Ixiii, Feb. 1873. 2 Wien. Akad. Ber., Band Ixiv, ii. 

 3 Cloetta, Vierteljahr. der nat. for Gesells. in Zurich, Band i, p. 205. 



